Piezo-electric crystal transformer



Oct, 27, 1931. A, McL, co so 1,829,234

PIEZO ELECTRIC CRYSTAL TRANSFORMER I Filed Jan. 25, 1927 m L 60 v 51 INVENTOR ALEXANDER McLEAN NKOLSON QQZ GW TTORNEY VIII/111E:

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Patented Oct. 27, 1931 PATENT OFFICE PIEZO-ELECTRIC CRYSTAL TRANSFORMER Application filed January 25, 1927. Serial No. 163,325.

This invention relates to piezo-electric crystal devices, and more particularly, to arrangements in which such devices are utilized as transformers, adapted for theconversion of relatively small potentials to large potentials and the like, and more particularly to such devices adapted to form means for coupling thermionic relays.

It is an object of this invention to provide arrangements whereby piezo-electric crystal devices may be arranged andassociated with each other in a manner to convert relatively small potential differences to relatively large differences and vice versa, and having what may be termed a ratio of transformation which may be controlled by predetermination and design of apparatus, either with or without adjustment in operation.

It is a further object of this invention to provide improved apparatus for utilizing a plurality of piezo-electric crystal devices ar ranged to work one into another with mechanical coupling, the different crystal devices being arranged in such a way as to have relatively different volumetric or linear deformations, whereby different potential differences may be developed on the various crystal devices.

It is still a further object of this invention to provide improved apparatus for mount ing and housing the piezo-electric crystal de vices for optimum operation with one another. Still other objects of this invention will be apparent from the specification.

The features of novelty which I believe to be characteristic of my invention are set forth with particularity in the appended claims. y invention itself, however, both as to its underlying application, eience to the specification and drawings, in which:

Fig. 1 is a front elevation of a transformer in accordance with my invention.

Fig. 2 is a top plan view thereof. I

will best be understood by refaccompanying principles and as to its practical Fig. 3 is a front elevation of a modified form of transformer according to my invention, showing a part of the apparatus broken away.

Fig. 4 is a circuit diagram, illustratingone application of a transformer according to my invention.

Fig. 5 is a view similar to Fig. 3 of a modified form of apparatus according to my invention.

In accordance with my invention, I provide a plurality of crystal devices of different operating characteristics, that is to say, one of which is more readily deformable or bendable than another, and I provide an arrangement whereby an electromotive force may be impressed upon the first crystal device to causeit to vibrate. A mechanical coupling is provided between the crystal devices whereby the vibrations of the first crystal device are transferred to the second crystal device. The arrangement may take the form of a lever arm attached to each device, so chosen as to give the effect desired: for instance, if it is desired to convert a relatively large current and small potential difference into a relatively small current at a high potential difference, different size crystals may be utilized, and the lever arms associated with each crystal so chosen that the motion of the first crystal, large crystal actuated by a large current at a low potential difference, may be multiplied and impressed upon the second crystal, which may be a relatively small crystal. The multiplication of the stresseseflected by the lever arm will stress the smaller crystal to a greater extent than the large crystal, and thereby relatively higher voltages are produced, since these voltages are a function of the s resses applied.

According to another form of my invention, the crystals may be arranged for direct stressing of one another without the intervention of'the lever arms: for example, a pluwhich may be a relatively rality of crystals may be arranged in line and an electromotive force impressed upon one or more thereof. If the crystals are properly oriented, as will be pointed out hereinafter, the expanding crystals will cause compression of the interposed crystals, and thereby produce electric charges thereon: and if the thus strained crystals are properly chosen, the ratio of the electroniotive forces iinpressed to those generated may be controlled as desired: for example. if torsionally vibrating crystals are desired to be utilized, crystals of different thicknesses may be chosen, whereby a corresponding mechanical force applied. will cause correspondingly greater deformations in the thinner crystal, and thereby cause the generation of a greater charge.

Crystals of different physical form having different resistances to the stresses involved, may be utilized: for example, it will be apparent that a. relatively thick square crystal would be less deformable under a given mechanical stress than a relatively thin crystal of the same material, that is. would have what I term a different phasestrain ratio. Also, crystals of different piezo-electric material may be utilized. whereby equal deformations produce unequal charges, and vice versa, the guiding principle being that an electromotive force may be impressed upon one crystal and converted thereby into a me hanical force which may be multiplied or divided through the medium of the lever arms and the like, and impressed upon second piezo-electrie crystal device so chosen that the stresses available produced the charges desired.

It will be understood. that in ace rdance with these prnciples, the transformers may be constructed with any desired ratio, including stepup, step-clown and one to one, which may be utilized in many ways as for example for coupling thermionic relays one to another as an improvement upon the arrangements described and claimed in my copending application entitled Piezo-electric coupling. Serial No. 155,896, filed Dec. 20, 1926,

and for coupling such relays to external cir cuit-s, either on the input or output side.

Referring now more particularly to Fig. l, I have shown an arrangement in which a pair of piezoelectric crystal devices. herein diagrammatically shown as liochelle salt crystals having the hour glass configuration particularly arranged for torsional vibration, are utilized.

In this figure, 1 designates a suitable base plate on which are mounted a pair of piezoelectric crystal devices 2 and 3, provided with suitable electrodes such for example as external electrodes -1- and 5 shown partly broken away, and adapted to be connected by links 6 and 7 of dilferent lengths. The links maybe connected to each otherby means of a suitable threaded pin 8 adapted to engage with cone spondingly tapped holes in the links, as more particularly shown in Fig. 2.

The crystal devices 2 and 3 may be secured in position by suitable bolts 11 and 12 passing through openings formed in the base plate in the crystals themselves and in the links. The depressions 9 and 10 will preferably be provided in the base plate and suilicient clearance will be allowed in the openings in the links to permit of optimum adjustment of the links. Suitable nuts 13 and 1% may be pro vided, engaging the bolts 11 and 12, by means of which the links may be tightly secured to the crystal device, and also the desired compression exerted upon the crystal for optimum operation. The bolts 11 and 12 may likewise be utilized as internal electrodes. In case the crystal device 3 is relatively smaller than the crystal device 2, a suitable spacing block 15 may be interposed between this crystal and the base plate 1.

If now an eletromotive force be impressed between external electrode 4 of crystal device 2 and internal electrode 11 the crystal will tend to rotate with respect to the bottom thereof in a direction depending upon the polarity of the impressed charge, thereby tending to rotate the top of the crystal device 3 thereof, the effect of which is to cause the production of a potential difference between the external electrode 5 and the internal electrode 12 depending upon the direction of the stress of the crystal. If, as already stated, the crystal device 3 be of such a nature that'it is more readily deformable than the crystal device 2, an electromotive force will thus be generated, which may be greater than that impressed upon the crystal device 2, and by properly choosing the nature, size and physical characteristics of the crystal and the length and arrangement of links, any practical desired ratio of transformation may be obtained.

Referring now more particularly to Fig. 3, I have shown an arrangement in which one crystal may work directly upon another without the interposition of a lever arm for obtaining mechanical multiplication of motion. In this figure, 50 designates a housing adapted to be secured to a suitable base plate 51, for example, by means of bolts A suitable spacing and supporting block 5- may be mounted upon the base plate 51 and adapted to receive a crystal. and wi h its axes of maximum expansion and contraction norma-l to the base plate 51. In the case of Rochelle salt crystals exhibiting the hour glass configuration, the particular axes of expansion and contraction corresponding to particular polarizations, are. set forth in my copending application, Serial No. 155,902. filed Dec. 20, 1926, entitled Orientation of component crystals in composite piezo-electhereof, the top of with respect to the bottom site phase with tric devices, but for the purpose of this application it may be stated that the crystal may be mounted with one of its hour glass diagonals vertical, as shown. A second supporting and spacing block 56 may be placed upon the apex or salient portion of the crystal, which spacer block will be formed to receive therein a second crystal 57, which may be fitted with a reinforcing and stress distributing block 58, adapted to be engaged by lower nut of screw thread 59 passing through housing 50. Leads may be connected to appropriate electrodes on each of the crystal devices, which elcc rodes may take any of the forms described in my application referred to above.

Leads may be passed through in any suitable way through the housing, as for example by being formed into a cable and carried through an opening in the side of the housing, which opening may be closed by suitable bushing 61. By means of the screw 59, the desired compression may be exerted to secure the crystals rigidly in position with the optimum pressure. If now an electromotive forcebeimpressed upon the electrodes of crystal 55, the crystal 55 will expand or contract along its vertical diagonal, thereby either forcibly compressing the crystal device 57, or relieving the compression thereupon and permitting it to expand. In any event, the crystal device 57, as will be seen, is mechanically deformed or stressed in synchronism with the crystal 55, but mechanically in oppo respect thereto: that is, when the crystal device 55 expands, the crystal device 57 contacts, and vice versa. It will be clear that by properly choosing the characteristics of the crystal device, the desired ratio or transformation may be obtained.

In Fig. 5 I have shown a transformer similar to that shown in Fig. 3 but in this case utilizing crystals of different piezo-electric material. For example, may indicate a crystal of Rochelle salt, while 66 indicates a crystal of quartz or other piezo-electric material. As with the arrangement shown in Fig. 3 an electrode system is provided for impressing the driving electromotive force upon the driving crystal and withdrawing the electromotive force generated in the driven crystal.

The transformer is capable of various uses: for example, as shown in Fig. 4, it may be utilized for coupling thermionic devices one to another in cascade, or for coupling the input or output circuits thereof to other sources of supply or loads: 20 designates a suitable source of electromotive force, which may be a microphone, an antenna, or the secondary of a piezo-electric transformer, such as already described. The source 20 is connected in the input circuit of thermionic relay 21, comprising for example, a control electrode 22, an anode 23, and a source of electrons such for example as filament 24 energized by a suitable source of power, as a battery. A suitable source of potential such as battery 25 will also be provided for maintaining the potential of the anodey23, and in the arrangement shown, a suitable choke 26 is provided in series therewith, to prevent ,th'eshort circuiting of; electrical. oscillations through the battery 25.

The primary of a piezo-elect-ric transformer as above described, may be connected in the output circuit, as for example by connecting the electrodes 4 and 11 of the device shown in F ig. 1 to the anode and cathode circuits respectively. It will be understood that the arrangement of Fig. 3 may likewise be so utilized. The secondary of the piezo-electric transformer may be connected in the input circuit of thermionic relay 31, and comprising control electrode 32, anode 33, and cathode 34, and having similarly asource of potential 35 in series with suitable choke 36 for maintaining the potential of the anode 33. If it is desired to utilize the second piezoelectric transformer, the corresponding electrodes 4 and 11 may be similarly connected to the anode 33 and cathode 34 of thermionic relay 31. Electrodes 5 and 12 may be connected to terminals 40 and 41, from which leads may be taken to any desired translating device.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made, as will be understood by those skilled in the art, without departing from the spirit and scope of my invention.

I claim:

1. A piezo-electric transformer comprising, in combination, .a piezo-electric crystal device, means for impressing electromotive forces thereon, a second piezo-eleetric crystal device associated with said first device, in a manner to be stressed by vibration of said first device, means for multiplying the motion of said first device interposed therebetween and means for withdrawing the electromotive force generated by said second crystal.

2. A piezo-electric transformer comprising, in combination, a piezoelectric crystal device having a predetermined phase-strain ratio, means for impressing electromotive forces thereon, to cause vibration of said device, a second piezo-electric crystal device having a phase-strain ratio different from that of said first crystal device associated with said first device in a manner to be stressed by vibration of said first device, means for multiplying the motion of said first device interposed therebetween and means for Withdrawing the electromotive force generated by said second crystal.

3. A composite piezo-electric crystal device comprising a plurality of piezo-electric ALEXANDER MQLEAN NICOLSON. 

